Capturing data defining a shape of 3-dimension contours, in particular of protrusions on base surfaces that are substantially flat is often required in industrial applications in order to perform quality control upon protrusions that have been fabricated in a defined manner like, e.g., glue points, glue beads, welds, coatings, etc.
Determining shape data or other specifying data that relates to a surface shape, e.g., of a volume of a protrusion is typically performed by a light section method.
Thus, a fanned light beam that is only fanned in one plane shines onto a surface to be examined and detected at an angle, typically an acute angle, to a direction of irradiation so that a shape of an image of the fanned beam on the surface facilitates detecting protrusions on the surface since the detected image shows a rise when the light beam fan that impacts in a line runs transversely over the protrusion.
Individual images of the light line on the object are captured in great numbers with short time intervals in between while the object moves in a transversal direction relative to the light line, so that its three-dimensional surface shape can be determined by sequentially assembling the individual elevation scans and/or parameters like height, volume, width, position of the protrusions associated therewith.
The typically artificially created protrusions shall be typically detected during a fabrication process of an object so that a very high detection speed and processing speed of this contour determination is required when, for example, the object runs with a speed of 600 m/min under the light line. When the detecting is performed, for example, by an off-the-shelf surface scanner with 512×512 pixels at 30 Hz thus 30 scans per minute, almost 8 million data sets have to be processed per second presuming only one data set per pixel. A data set, however, includes at least two individual data fields (position and light intensity), sometimes even more.
Accordingly, a minimum time between the individual scans caused by the optical sensor as well as the processing speed of the image data thus determined by the subsequent electronic processing unit can be a limiting factor.
The minimum time between the individual scans is a sum of an exposure time of the sensor that is always required and essentially always has the same length and a time period required for reading the image data from the optical sensor into the subsequent processing unit, wherein the reading time depending on the sensor type can be a function of a number of data sets read out, thus pixels read out.
In this context various types of flat optical sensors have to be differentiated:                For all flat optical sensors, it can be determined before starting the reading that only the image data of particular lines and/or columns of the typically grid arranged pixels of the flat optical sensor shall be read or also only the image data of reading windows within the sensor surface is predetermined before the reading, in particular before capturing the image wherein the reading windows are predetermined by line numbers and/or column numbers.        For particular sensor types it is possible to start reading the image data at one of the ends of a line shaped image of the light line which extends e.g., approximately in line direction and to initially predetermine and sequentially read only a relatively small portion of the window portion of the image data that extends transversely to the image as a function of a predetermined position and orientation of a beginning of the image, namely a portion in which the image will most likely be arranged as a function of a position in the preceding window portions.        
Both facilitates keeping a volume of image data to be read out at an optimum low level for each scan, however, the latter sensor type is typically not available or not available with the desired parameters and has other disadvantages.
The processing speed of the read image data is a function on the one hand side of a data volume to be processed and on the other hand side a function of a type of processing operations and their number.
Ideally a time for processing a data volume of a scan is as short or shorter than a minimum time between individual scans or at least a minimum time that is predetermined by the processing process between sequential data writing operations of the individual scans into the processing unit is as short or shorter than the minimum time between the scans in that processing the read image data is performed sequentially so that a time requirement for individual processing steps is respectively arranged below a minimum time between the scans.
The scan frequency thus generated shall be high enough eventually so that individual scans on the object are performed with a short spatial distance between each other for a maximum running speed of the object to be scanned, thus e.g. the production machine a quasi-seamless checking of surface data that is of interest is facilitated.
Using the example of controlling a glue bead that is applied to a surface in a continuous process a scan is performed along the glue bead every millimeters and determines which height, width and/or cross-sectional surface the glue bead had at each individual scan.
In spite of different consistency of the glue and of inertia of nozzles applying the glue bead it is assured that no voids can occur in the glue bead which can influence a subsequent quality of the glue joint.